Bikes are very resilliant to rain and will cary on for decades of daily use in wet climates.

If you take the seat out, rain will gather more quickly in the BB shell,
I prep my bike for wet winters by:
Packing the bearings full of grease. Im not sure this is recommended but it definately prevents ingress of crud.
Greasing all relevant metal-metal contact (threads, seatpost, stem etc).
Squirting rust-preventer inside steel frames.
Waxing frame, exposed cable wire, esposed bolt heads, exposed pedal spindles, anywhere likely to rust or corrode
Using full-length cable housings, well greased inside.

Beware of places where water can gather, esp BB shell and some cable outers (esp rear mechs using TT cable routing)